1. Field of the Invention
The present general inventive concept relates to an auto stabilization method and a photographing apparatus using the same. More particularly, the present general inventive concept relates to an auto stabilization method to compensate for hand tremor according to a driving characteristic of a photographing element employed in a photographing apparatus, and a photographing apparatus using the same.
2. Description of the Related Art
Generally, hand tremor of a photographing apparatus is generally compensated for by compensation of divergence of an optical axis due to vibration by driving a lens, compensation by driving a photographing element where an image is converged, and compensation by processing a signal of a photographed image.
Compensating for hand tremor by lens driving is inefficient for a compact and light apparatus, due to non-linearity of a lens in an optical compensation, and its requirement for a driving lens in a lens barrel. Compensating by signal processing may be the most appropriate for an economic, compact and light apparatus, as it requires no additional hardware. However, this method has fluctuation of compensation accuracy depending on the respective algorithm employed for signal processing, and has degraded performance compared to an optical compensation.
Compensating by driving a photographing element is an example of optical compensating. This method requires a driving system to drive a photographing element, but is far more efficient for a compact and light apparatus, than compensating by driving a lens.
One of the ways to drive a photographing element is to use a smooth impact drive mechanism (SIDM), which drives a photographing element by use of a piezo-electric element. SIDM adjusts a moving distance of a photographing element, by using a voltage applied to a piezo-electric element. In particular, SIDM gradually moves a photographing element to a desired location, repeatedly in an ultrasonic level cycle. Although the photographing element mounted on a rotary axis moves along, when the piezo-electric element is expanded gradually, the piezo-electric element may contract too fast for the photographing element to follow.
Accordingly, SIDM using a piezo-electric element has low responsiveness, and although it uses ultrasonic waves, SIDM may have a high frequency noise. Technical skills and costs are also required, to stack piezo-electric elements of a desired expansion and contraction. If a hand tremor compensation mechanism is not employed, additional structures such as a latch to fix a driving system are required, which is inappropriate for a compact and light apparatus.
Meanwhile, a method using a voice coil motor actuator (VCMA) has been proposed, modeling a free mass system, to drive a photographing element.
FIG. 1 illustrates a voice coil motor driving unit to drive a photographing element. Referring to FIG. 1, the voice coil motor driving unit includes a main frame 10, a yaw-axis driving frame 20 on the main frame 10, and a pitch-axis driving frame 30 mounted on the yaw-axis driving frame 20 and having a photographing element mounted thereon.
When an electric current flows through a coil of an actuator mounted on the main frame 10, the yaw-axis driving frame 20 having a magnet mounted thereon, and the pitch-axis driving frame 30 having a magnet are driven in a two-dimension with respect to the main frame 10 according to a magnetic force formed between the coil and the magnet. A ball 40 is inserted between the main frame 10 and the driving frames 20 and between the driving frames 20 and 30 to reduce friction. The ball 40 is moved along a ball guide 45 formed on corresponding surfaces of the main frame 10, the yaw-axis driving frame 20, and the pitch-axis driving frame 30 to accommodate the ball 40.
A photographing apparatus adopting a VCMA modeling a free mass system, has a smooth surface illuminance, and thus can provide advantages such as compactness and low power consumption, if a friction is not considered.
However, because no structure is provided to support the driving frames 20, 30 during a time that a control input is not applied, dynamic characteristic of a voice coil motor driving unit changes according to a posture of an apparatus due to influence of gravity.
Furthermore, displacement of the driving frames 20, 30 reaches maximum degree or it is slowed, if the ball guide 45 has a rough surface illuminance. For example, if the ball 40 is at an edge of the ball guide 45, the ball 40 would hit a wall of the ball guide 45 by the application of a control input, and as a result, the driving frames 20, 30 are not moved smoothly.